The present invention relates to a cantilever for a pickup cartridge used in a sound recording-reproducing system.
In general, the cantilevers for pickup cartridges must be light in weight in order to reduce the effective mass viewed from the tip of a stylus and must be also strong and rigid so as to avoid divide vibrations. To these ends extensive studies and experiments have been made.
A prior art cantilever for a pickup cartridge is made of a pipe of an aluminum alloy. In order to obtain required strength, the pipe must have a large diameter and a thick wall and consequently is very heavy, so that the effective mass of a vibrator is increased. In order to solve these problems, there has been proposed to use a pipe made of titanium because the latter has excellent mechanical strength so that both the diameter and wall thickness may be reduced and consequently the weight may be reduced. However, even with the titanium pipe sufficient strength and rigidity cannot be attained.
In order to attach a stylus tip, one end of a cantilever is pressed flat, a hole is formed through the flattened portion and the stylus tip is forcibly fitted into this hole. In this case, the cantilever is annealed so that the decrease in strength and rigidity results. In order to solve this problem, the cantilever with the stylus tip is subjected to the oxidation process, but satisfactory strength and rigidity still cannot be attained because the oxidation process results in the increase in rigidity and Young's modulus only by 10%. Furthermore the control of oxidation of the cantilever is difficult and in the extreme case the cantilever becomes brittle.
Because of these unsatisfactory cantilevers, the conventional pickup cartridges exhibit the so-called drooping phenomenon. That is, their frequency response drops in the range between 2 and 10 KHz below the high resonance frequency f.sub.0 (which is in general between 10 and 40 KHz). Thus the flat frequency response curve cannot be obtained. Furthermore their transition characteristics which determine the degree of trackability are not satisfactory.